I. Field of the Invention
The present invention relates to a method for quantitative analysis of atomic components of materials by LIBS spectroscopy measurements without calibration.
II. Related Art and Other Considerations
Quantitative and real time analysis of the elementary composition of materials is of great interest in many fields, from industrial production to environment diagnostics, from on-line control of product quality to monitoring of industrial exhaust.
At present, the most widespread systems of quantitative analysis require sampling of the materials, with a consequent off-line characterisation. Generally, this procedure involves an increase of the times for the acquisition of the necessary data and, therefore, of costs and risks.
The LIBS (Laser Induced Breakdown Spectroscopy) or LIPS (Laser Induced Plasma Spectroscopy) technique is a technique for quick analysis of a sample""s elementary constituents, that can be applied in situ and gives results in real time. Current systems based on LIBS rely on calibration curves in order to determine the concentration of the various elements [D. A. Cremers, M. J. Ferris and M. Davies: xe2x80x9cTransportable Laser Induced Breakdown Spectroscopy (LIBS) instrument for field-based soil analysisxe2x80x9d. SPIE Vol. 2835 (190-200) 1996].
The present invention proposes a method based on LIBS technology for determining the concentration of the various elements present in the sample, without use of calibration curves.
The method of the present invention and embodiments thereof are defined in the claims.
The application of the present method allows:
i) to perform quantitative analysis by the LIBS technique, without need of reference samples, and without calibrations;
 less than The article of B. J. Goddard xe2x80x9cMaterials analysis using laser-based spectroscopic techniquesxe2x80x9d, Transaction of the Institute of Measurement an Control, 1991, UK, vol. 13, no. 3, pages 128-139, discloses several laser based spectroscopic methods capable of detecting low concentrations of a particular element. In the case of a LIBS methods, for a system in LTE it is possible to derive the relative concentrations of the elemental constituents by measuring line intensities, greater than 
 less than  less than The patent application WO 97/15811 relates to spectroscopic determination of the concentration of atomic species in samples. The concentration of the atomic species to be determined is then derived from the known emission intensity of a predetermined concentration of that specie in the sample at the measured temperature, a quantity which would have been measured prior to the determination of the unknown concentration, and the actual measured emission from the unknown species, or by this latter emission and the emission intensity of a species having known concentration within the sample such as nitrogen for gaseous air samples, greater than  greater than 
ii) to reduce measurement costs and times, because the method is self-consistent (the experimental quantities that are necessary to determine the concentrations are absolute quantities that are obtained from the same measure).